U.S. paleontologists have described a new giant species of lizard that lived in what is now Myanmar up to 40 million years ago.

Reconstruction of Barbaturex morrisoni (Angie Fox / Nebraska State Museum of Natural History, University of Nebraska-Lincoln)

The lizard, named Barbaturex morrisoni, was a plant-eater, like present-day iguanas.

“In today’s world, plant-eating lizards like iguanas and agamids are much smaller than large mammal herbivores. The largest lizards, like the giant, carnivorous Komodo dragon, are limited to islands that are light on mammal predators. It is not known, however, if lizards are limited in size by competition with mammals, or by temperatures of modern climates,” said Dr Jason Head of the University of Nebraska-Lincoln, first author of a paper reporting the discovery in journal Proceedings of the Royal Society B.

At some 60 pounds and six feet in length, Barbaturex morrisoni was one of the largest of its kind – making it a veritable ‘king’ of land-dwelling lizards.

“Barbatus is from the Latin, which means ‘bearded,’ and rex, means ‘king’ – so the name refers to the presence of ventral ridges along the underside of the mandible, as well as the giant size of the lizard,” explained senior author Dr Russell Ciochon, a paleoanthropologist with the University of Iowa.

“The species name honors vocalist Jim Morrison. We did take some liberty in naming the new species after rock legend Jim Morrison, who is known as the Lizard King.”

Barbaturex morrisoni lived in an ecosystem with a diversity of both herbivorous and carnivorous mammals during a warm age in Earth’s history when there was no ice at the poles and atmospheric carbon dioxide levels were very high.

The creature was larger than most of the mammals with which it lived, suggesting that competition or predation by mammals did not restrict its evolution into a giant.

“We think the warm climate during that period of time allowed the evolution of a large body size and the ability of plant-eating lizards to successfully compete in mammal faunas,” Dr Head said.

“You can’t fully understand the evolution of ecosystems in the modern world without looking at the ones that preceded them. We would’ve never known this by looking at lizards today. By going back in time using the fossil record, we can find unique information on the origin of modern ecosystems.”